The invention relates generally to improvements in strap tensioners, particularly hand held, power strap tensioning tools.
It is known generally to tension strap applied about a load with a power or manually operated hand held tensioning tool. The tensioning tools comprise generally a gear housing with a feed wheel protruding from a side portion thereof for engaging and tensioning strap disposed between the feed wheel and a foot of the tool.
In some tensioning tools, the foot is pivotally coupled to the gear housing and a torsional foot spring biases the pivotal foot toward the feed wheel to engage the strap during tensioning. The PN-114 & PNR-114 push type tensioning tools available from ITW Signode, Glenview, Ill. for example have a breaker foot pivotally biased toward a feed wheel by a torsional foot spring to engage a strap portion between the feed wheel and an anti-friction device mounted in the foot during tensioning. See also, U.S. Pat. No. 3,249,131 entitled "Power Strap Tensioning Tool".
Some tensioning tools other than push type tools also comprise a foot biased by a torsional foot spring toward a feed wheel during strap tensioning. These tools include, among others, strap on strap tensioning tools. In strap on strap tensioning tools, however, gripper teeth are mounted in the foot, instead of the plug or roller used in push type tools, for engaging a lower strap portion during tensioning.
The torsional foot spring in the tensioning tool of U.S. Pat. No. 3,249,131 and other tools is disposed generally about a machined pivot shaft in a recess between the foot and the gear housing where the torsional foot spring is largely exposed on an upper portion of the tool. The exposed torsional foot spring however is particularly vulnerable to damage, for example from rough handling of the tool, which is common in the industry. The exposed spring also accumulates debris and particulate matter, which tends to interfere with the smooth pivoting action of the tool.
The torsional foot springs in known tensioning tools have a relatively short life span, and thus require frequent replacement. In some tools, the torsional foot spring degrades noticeably after approximately 1000 operation cycles. The short life span results partly from the relative inefficiency of torsional springs generally, and from the limitation on the number of turns or coils that will fit in the limited space between the gear housing and the pivotal foot of the tool. Also, many torsional foot springs are specialty parts, which are relatively costly.
Push type tensioning tools, for example the tools discussed in U.S. Pat. No. 3,249,131 entitled "Power Strap Tensioning Tool", also comprise a breaker nose pivotally coupled to and biased toward a breaker foot by a nose torsional spring. The breaker nose engages a metal clip disposed about overlapping strap portions during tensioning, and is pivotal to accommodate straps having different thicknesses between the breaker nose and the foot. The torsional nose spring, however, is subject to the same disadvantages discussed above in connection with the torsional foot spring.
In the tensioning tools discussed above, the foot pivots about a machined pivot shaft coupled to the gear housing. In push type tensioning tools, the breaker nose and the roller mounted in the foot also pivot about machined pivot shafts. The machined pivot shafts are rotationally fixed, often by a roll pin or by screw thread engagement with some fixed structure. The fixed pivot shafts are however difficult to assemble and maintain, and tend to wear relatively quickly. Also, many prior art pivot shafts are specialty parts having different diameters machined along the axial dimension thereof, and are thus relatively costly.
In known prior art push type tensioning tools, the gear housing has at least two access openings at least one of which has an exposed cover plate for assembly and maintenance. In the past, the multiple access openings were necessary to install components in the gear housing, including for example a drive gear and shaft coupled to the feed wheel and bearings associated therewith. In the tool of U.S. Pat. No. 3,249,131, for example, two oversized radial and thrust load bearings are installed in the gear housing from an opening on a side portion thereof and a worm wheel is installed from an opening on the bottom portion thereof. During use, however, fasteners that retain the exposed cover plate on the tool tend to loosen, resulting in separation of the cover plate therefrom. It is not uncommon for the tools to be operated without a cover plate, exposing the gear housing interior to the environment.
The present invention is drawn toward advancements in the art of strap tensioning tools.
An object of the invention is to provide novel strap tensioning tools that overcome problems in the art.
Another object of the invention is to provide novel strap tensioning tools that are economical.
Another object of the invention is to provide novel strap tensioning tools that are more reliable, have fewer components, and are easier to operate, assemble and maintain.
A further object of the invention is to provide novel strap tensioning tools having improved pivotal foot assemblies.
Another object of the invention is to provide novel strap tensioning tools having a gear housing with only a single access opening and corresponding cover plate.
Another object of the invention is to provide novel strap tensioning tools having a foot pivotally coupled to a gear housing and biased by a compression foot spring toward a feed wheel protruding from the gear housing.
Another object of the invention is to provide novel strap tensioning tools having a nose pivotally coupled to a foot and biased by a compression nose spring toward a strap support portion of the foot.
A further object of the invention is to provide novel strap tensioning tools having one or more of a gear housing with a foot pivotally coupled thereto by a rotatably supported foot pivot member, a nose pivotally coupled to the foot by a rotatably supported nose pivot member, and a foot roller rotatably coupled to the foot by a rotatably supported roller pivot member, and combinations thereof.
Yet another object of the invention is to provide novel strap tensioning tools having a foot coupled to a gear housing, and a nose pivotally coupled to and biased toward the foot. The nose having a strap engagment portion biased toward a strap support portion of the foot and separated therefrom by a gap to facilitate insertion of a strap portion therebetween.
Another object of the invention is to provide novel strap tensioning tools having a foot pivotally biased relative to a gear housing by a foot biasing member, preferably a compression spring, that is protected from the environment.
Still another object of the invention is to provide novel strap tensioning tools having a foot pivotally coupled to a gear housing, and a lever extending from the foot and aligned substantially along an axis of the gear housing.